How to save a SSL certificate and create a virtual

I have a Rails app, which uses the gem Rails Let's Encrypt to generate SSL certificates for custom domains.

The gem is really simple to use. After the installation/configuration, I can generate a certificate and the data will be stored in the database.

I want to save the certificate CRT and the certificate KEY in the respective NGINX folder: /etc/nginx/ssl/

After that, I want to :

Copy the file /etc/nginx/sites-available/default and save with name /etc/nginx/sites-available/customdomain.com
Change the file customdomain.com with this:

Content:

server {
    listen 80;
    listen 443 ssl;
    server_name www.customdomain.com;
    ssl_certificate /etc/nginx/ssl/customdomain.crt;
    ssl_certificate_key /etc/nginx/ssl/customdomain.key;
    passenger_enabled on;
    root /home/ubuntu/myapp/current/public;
    gzip on;
    gzip_http_version 1.1;
    gzip_vary on;
    gzip_comp_level 6;
    gzip_proxied any;
    gzip_types text/plain text/css application/json application/javascript application/x-javascript text/javascript
    gzip_disable "msie6";
    location ^~ /assets/ {
        expires max;
        add_header Cache-Control public;
    }
}

Create a link to this file in sites-enabled with this code: sudo ln -s /etc/nginx/sites-available/customdomain.com /etc/nginx/sites-enabled/
Restart nginx: sudo service nginx restart

I did these steps manually and the SSL works fine. How to do this programmatically?

Remember, the steps starts when, with Rails, I generate a certificate. There must be some way to execute these steps. I appreciate any help! Tks!

My environment:

ruby -v: ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]
rails -v: Rails 4.2.3
nginx -v: nginx/1.8.0
passenger -v: Phusion Passenger version 5.0.10
Ubuntu 14.04.2 LTS
Amazon EC2 instance (without load balancer, because LB requires only one certificate in the https)

EDIT 1

Perhaps, there's a way using wildcard configuration. Rather than create one virtual host for each domain, I create only one file, like that:

/etc/nginx/sites-enabled/wildcard

In this file, I have a modification like that:

server_name {{customdomain_url}};
ssl_certificate /etc/nginx/ssl/{{customdomain}}.crt;
ssl_certificate_key /etc/nginx/ssl/{{customdomain}}.key;

If it is possible, is better, because the job is only save the certificate files. And will not require the nginx restart.

EDIT 2 - The way

I created a shell script in /user/local/bin/myscript.sh and, in this script, I create a vhost file in /etc/nginx/sites-available/ to test. In rails console, I run the code: sudo /user/local/bin/myscript.sh mydomain.com and the shell script create correctly the file.

It was a test, but works. I will to create the final version and post here the final solution.